1. Field of the Invention
The present invention relates to a laser processing robot. The present invention also relates to a robot system including the laser processing robot.
2. Description of the Related Art
In a laser processing robot system in which an industrial robot carries out a laser processing, it is known that an optical fiber can be used as a transmission path for supplying a laser beam from a laser oscillator to a laser processing tool attached to a wrist portion of a robot mechanical section (referred to as a “manipulator” in this application). In this robot system, the optical fiber generally has a large minimum-allowable radius-of-curvature and is laid outside the manipulator, as an umbilical member in the form of a cable or a containing conduit, so as to have a certain degree of freedom for maintaining a bending radius larger than the minimum-allowable radius-of-curvature. In this arrangement, during a period when the manipulator operates in a laser processing, the laying configuration of the umbilical member considerably varies due to the operation of the manipulator, so that the umbilical member may be excessively pulled to be entangled with the arm section or other peripheral members, or may be excessively loosened to reduce the output power of the laser beam due to a variation in curvature, which may lead to a malfunction in a processing operation.
In order to solve the problems associated with the optical fiber layout in the laser processing robot system, it is conventionally proposed to accommodate the optical fiber (or the umbilical member) within the arm section of the manipulator. For example, Japanese Patent Publication No. 2606011 (JP-B-2606011) discloses that an optical fiber connected to a laser torch attached to a wrist portion at the distal end of an articulated robot is arranged within a hollow portion of a rotation shaft of an arm having the wrist portion to extend along a rotation axis of the shaft. On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 2003-200376 (JP-A-2003-200376) discloses that a cable for supplying power, signal, material, etc. to an end effector attached to a wrist portion of an industrial robot is introduced into an interior of an arm through an inlet port formed at a lateral side of the arm and is drawn out from an opening formed at a position intersecting the axis of a rotation shaft of the wrist portion to extend to the end effector.
In the construction as disclosed in JP-B-2606011, the optical fiber is passed through the hollow portion of the rotation shaft from the rear end of the arm having the wrist portion so as to be introduced into the interior of the arm, and then extends directly to the laser torch at the distal end. The laser torch projects from the wrist portion in a direction perpendicular to the axis of the rotation shaft of the arm, so that the optical fiber extends to be bent or turned at generally 90° at a location just before the laser torch. In this construction, it may be difficult to ensure or maintain the minimum-allowable bending radius of the optical fiber at a bent region just before the laser torch. In this connection, although it is possible to ensure the minimum-allowable bending radius of the optical fiber just before the laser torch by increasing the projecting length of the laser torch from the wrist portion, there may be another problem in this measure such that the outer dimensions of the robot, in particular in the region of the end effector, are increased.
Also, in the construction as disclosed in JP-A-2003-200376, the end effector projects in a direction perpendicular to the axis of the rotation shaft of the wrist portion, so that, in order to maintain the minimum-allowable bending radius of the cable just before the end effector, the wrist portion is formed into a two-branch structure so as to expose a portion of the cable to the outside of the wrist portion. If the cable contains an optical fiber, the exposed portion of the cable may give rise to the above-described problems due to the excessive entanglement or loosening. In this construction, there may also be a problem in that the outer dimensions of the region of the end effector are increased.